U.S. patent application number 15/099666 was filed with the patent office on 2016-08-11 for systems and methods for providing a self-adjusting light source.
The applicant listed for this patent is Stack Labs, Inc.. Invention is credited to Jovi Gacusan, Neil Joseph.
Application Number | 20160234907 15/099666 |
Document ID | / |
Family ID | 56566353 |
Filed Date | 2016-08-11 |
United States Patent
Application |
20160234907 |
Kind Code |
A1 |
Joseph; Neil ; et
al. |
August 11, 2016 |
Systems and Methods for Providing A Self-Adjusting Light Source
Abstract
System, methods, and apparatus, including devices and software,
for providing self-adjusting light sources. In one aspect, a
lighting unit includes one or more LEDs and an ambient light
sensor. The light sensor measures ambient light in synchronization
with intermittent off periods of light generated by the LEDs. For
example, the LEDs in the lighting unit can be driven by a pulse
width modulated signal that turns on and off the LEDs in an
alternating manner, and the ambient light can be measured when the
LEDs are turned off. In some implementations, a compact lighting
unit, such as a light bulb, is provided that can be easily attached
to standard light fixtures and can efficiently control its own
brightness based on ambient light conditions.
Inventors: |
Joseph; Neil; (Sunnyvale,
CA) ; Gacusan; Jovi; (Sunnyvale, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stack Labs, Inc. |
Sunnyvale |
CA |
US |
|
|
Family ID: |
56566353 |
Appl. No.: |
15/099666 |
Filed: |
April 15, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14288911 |
May 28, 2014 |
9345098 |
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15099666 |
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61956028 |
May 31, 2013 |
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61956029 |
May 31, 2013 |
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61958702 |
Aug 5, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05B 45/46 20200101;
H05B 45/20 20200101; H05B 47/11 20200101; Y02B 20/40 20130101; H05B
47/19 20200101; H05B 45/22 20200101 |
International
Class: |
H05B 33/08 20060101
H05B033/08; H05B 37/02 20060101 H05B037/02 |
Claims
1. A lighting unit, comprising: a lighting unit configured to emit
light; a driver connected to the lighting unit configured to
provide current to the lighting unit; and a light sensor integral
to the lighting unit configured to sense a surrounding of the
lighting unit and to provide a light intensity signal based on the
sensed surrounding.
2. The lighting unit of claim 1, further comprising: a controller
configured to provide a drive control signal to the driver, wherein
the drive control signal includes intermittent periods during which
the intensity of the light emitted by the LED component is lowered;
and a measuring component configured to measure the light intensity
signal from the light sensor in synch with the drive control signal
and to output the measured light intensity.
3. The lighting unit of claim 2, wherein the controller is
configured to adjust the drive control signal based on the measured
light intensity and a user setting.
4. The lighting unit of claim 1, wherein the lighting unit and the
light sensor are components of a single light bulb.
5. The lighting unit of claim 1, further comprising a housing
configured to attach the lighting unit to a light fixture and to
couple external power to the driver.
6. The lighting unit of claim 5, wherein the housing has a bulged
reflector (BR) design or a parabolic aluminized reflector (PAR)
design.
7. The lighting unit of claim 5, wherein the housing includes the
light sensor and the lighting unit.
8. The lighting unit of claim 1, wherein the lighting unit
comprises one or more organic light emitting diodes (OLEDs).
9. The lighting unit of claim 1, wherein the lighting unit includes
LEDs emitting light with different colors, and wherein the lighting
unit is configured to enable shifting a color of the light emitted
by the LED component based on a signal from the driver.
10. The lighting unit of claim 9, wherein the lighting unit is
configured to enable the shifting of the color by changing a
wavelength of light emitted or by filtering light emitted.
11. The lighting unit of claim 1, wherein the light sensor includes
a photopic sensor configured to provide a light intensity signal
that approximates a response of the human eye.
12. The lighting unit of claim 1, wherein the light sensor includes
a photodiode or a photoresistor.
13. The lighting unit of claim 1, wherein the lighting unit and the
light sensor are positioned to limit an amount of light from the
lighting unit that is directly received by the light sensor.
14. The lighting unit of claim 2, wherein the controller is
configured to provide a pulse width modulated drive control signal
to the driver to turn on and off the current to the lighting unit
in an alternating manner.
15. The lighting unit of claim 14, wherein the measuring component
is configured to measure the light intensity signal when the pulse
width modulated drive control signal turns off the current to the
one or more light emitting diodes.
16. The lighting unit of claim 15, wherein the LED controller is
further configured to modify the pulse width modulated drive
control signal to turn off the current to the lighting unit when
the light intensity measurements are performed.
17. The lighting unit of claim 14, further comprising a
synchronization mechanism configured to generate a measurement
synch signal to synchronize the pulse width modulated drive control
signal with the light intensity measurements in the measuring
component.
18. The lighting unit of claim 17, wherein the measurement synch
signal includes a periodic signal.
19. The lighting unit of claim 17, wherein the measurement synch
signal includes a pseudo-random signal.
20. The lighting unit of claim 2, further comprising an occupancy
sensor configured to provide an occupancy signal to the measuring
component, wherein the measuring component is further configured to
provide occupancy measurements for the controller based on the
occupancy signal.
21. The lighting unit of claim 1, further comprising a non-light
environment sensor, wherein the lighting unit is configured to
adjust a color of the light emitted based on a signal from the
non-light environment sensor.
22. The lighting unit of claim 1, wherein the lighting unit
includes an LED component including one or more light emitting
diodes (LEDs).
23. The lighting unit of claim 1, wherein the light sensor is an
infrared light sensor.
24. The lighting unit of claim 1, wherein the lighting unit
comprises an A, BR, R, PAR, MR, PL, AR, A, B, S, F, T, GT, P, K,
tubular, pendant, troffer, can, or molded fixture style
fixture.
25. A method for operating a lighting unit configured to emit light
and a light sensor integral to the lighting unit configured to
sense a surrounding of the lighting unit, the method comprising:
providing current to the lighting unit; controlling the current to
the lighting unit using a drive control signal; providing a light
intensity signal based on the sensed surrounding the light sensor;
and performing measurements of the light intensity signal from the
light sensor.
26. The method of claim 25, further comprising using the
measurements of the light intensity signal to adjust the drive
control signal.
27. The method of claim 26, wherein using the measurements of the
light intensity signal includes processing the measurements to
determine whether the brightness of the lighting unit should be
changed.
28. The method of claim 25, wherein adjusting the drive control
signal includes receiving a user setting and adjusting the drive
control signal in accordance with the received user setting.
29. The method of claim 25, wherein the method further comprises:
providing an occupancy signal; and adjusting the drive control
signal includes adjusting the drive control signal based on the
occupancy signal.
30. The method of claim 25, wherein the method further comprises:
adjusting the drive control signal to shift a color of the light
emitted by the lighting unit.
31. The method of claim 25, wherein performing measurements of the
light intensity signal from the light sensor includes generating a
measurement synch signal and performing the measurements in
accordance with the measurement synch signal.
32. The method of claim 31, wherein performing the measurements in
accordance with the measurement synch signal includes modifying one
or more intermittent periods in the drive control signal.
33. A light bulb, comprising: a lighting component configured to
emit light based on a received drive signal; and a measuring
component integral to the light bulb configured to sense a
surrounding the light bulb; wherein a driver is configured to
modify the drive signal based on the sensed surrounding and a light
level setting.
Description
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 14/288,911, filed May 28, 2014, entitled
"Systems and Methods for Providing a Self-Adjusting Light Source,"
which claims the benefit of priority to the following U.S.
Provisional patent applications: Ser. No. 61/956,028 filed May 31,
2013, entitled "Method for adjusting light intensity of a lightbulb
within the enclosure," the entirety of which is incorporated by
reference herein; Ser. No. 61/956,029 filed May 31, 2013, entitled
"Light sensor in a light bulb to measure and control the intensity
of illumination and motion detection," the entirety of which is
incorporated by reference herein; and Ser. No. 61/958,702, filed
Aug. 5, 2013, entitled "Method for wireless control of a light
bulb." The entirety of all of these applications is incorporated by
reference herein.
TECHNICAL FIELD OF THE INVENTION
[0002] This disclosure relates to light sources and, in particular,
to controlling the light sources based on ambient light
measurements.
BACKGROUND
[0003] The U.S. Energy Information Administration estimated that,
in 2011, electricity used for lighting by the residential and
commercial sectors was equal to about 17% of the total electricity
consumed by both of these sectors and about 12% of total U.S.
electricity consumption. Thus, saving energy consumed by lighting
remains an important priority.
[0004] One way to save energy consumed by lighting is using light
bulbs that are more efficient than the traditional incandescent
lamps. For example, compact fluorescent lamps (CFLs) and light
emitting diodes (LEDs) offer lighting characteristics comparable to
the incandescent lamps, but with less power consumption and longer
product lifetime.
SUMMARY
[0005] A system, in one aspect, provides a lighting unit that
measures ambient light in synchronization with intermittent periods
when the light emitted by the unit is temporarily dimmed or turned
off. Thus, the lighting unit can control its own overall brightness
based on the measured ambient light. For example, the lighting unit
can have LEDs driven by a pulse width modulated signal that turns
on and off the LEDs in an alternating manner, and the ambient light
can be measured when the LEDs are turned off. In another aspect, a
system provides a self regulating lighting unit, such as a light
bulb, that can be attached to standard light fixtures and controls
its own brightness based on ambient light conditions.
[0006] In general, in one aspect, a system provides a lighting unit
that includes, in part, an LED component having one or more light
emitting diodes (LEDs) to emit light from the lighting unit, and an
LED driver connected to the LED component to provide current to the
one or more light emitting diodes. The lighting unit further
includes a light sensor, an LED controller and a measuring
component. The light sensor is configured to receive light from a
surrounding of the lighting unit and to provide a light intensity
signal based on the received light. The LED controller is
configured to provide a drive control signal to the LED driver,
wherein the drive control signal includes intermittent periods
during which the intensity of the light emitted by the LED
component is lowered. The measuring component is configured to
measure the light intensity signal from the light sensor in synch
with the intermittent periods in the drive control signal and to
provide the measured light intensity to the LED controller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a schematic block diagram illustrating a lighting
system according to one embodiment of the disclosure.
[0008] FIG. 2 is a schematic block diagram illustrating a lighting
unit according to one embodiment.
[0009] FIG. 3 is a schematic block diagram illustrating a measuring
component for a lighting unit according to one embodiment.
[0010] FIG. 4 is a schematic block diagram illustrating an LED
controller for a lighting unit according to one embodiment.
[0011] FIG. 5 is a schematic block diagram illustrating a system
for intermittent driving of LEDs in a lighting unit according to
one embodiment.
[0012] FIGS. 6 and 7 are schematic diagrams illustrating signals in
a lighting unit according to different embodiments.
[0013] FIG. 8 is a schematic flow chart illustrating a method for
operating a lighting system according to one embodiment.
[0014] FIGS. 9A, 9B and 9C are schematic diagrams illustrating
implementations of compact lighting units according to different
embodiments.
DETAILED DESCRIPTION
[0015] FIG. 1 is a schematic block diagram that illustrates a
lighting system 100 according to one embodiment of the disclosure.
The lighting system 100 includes a power source 110, a light
fixture 120, and a lighting unit 130. The power source 110 provides
electric power to the lighting unit 130 through the light fixture
120 that is configured to receive and hold the lighting unit 130 in
place. The lighting unit 130 includes an intermittent light source
132 that uses the received electric power to emit light 190. The
lighting unit 130 also includes an ambient light meter 134 and a
synchronization mechanism 136 that are used to measure a level of
ambient light 195 at the location where the light fixture 120 and
the lighting unit 130 are installed. Based on the measured level of
the ambient light 195, the lighting unit 130 adjusts the brightness
of the emitted light 190. Thus, power consumed from the power
source 110 can be saved.
[0016] In the lighting unit 130, the light 190 emitted from the
intermittent light source 132 is modulated by including relatively
short intermittent time periods when the light 190 is turned off or
dimmed, and the synchronization mechanism 136 synchronizes the
measurement of the ambient light 195 by the ambient light meter 134
with these intermittent time periods of the light source 132. For
example, the level of the ambient light 195 can be measured by the
light meter 134 during the short time period when the intermittent
light source 132 does not emit the light 190. Advantageously, the
intermittent time period can be short enough so that the human eye
would not directly notice the lack of the emitted light 190
(although the effect of the intermittent period may be sensed by
the human eye as a lowered level of average brightness).
[0017] In the lighting system 100, the intermittent modulation of
the emitted light 190 and the synchronized measurement of the
ambient light 195 can be repeated according to a predetermined
scheme, for example, periodically or randomly. Thus, the ambient
light 195 can be measured in a manner somewhat analogous to an
"inverse" stroboscope where the measurements are made during the
periods when the emitted light 190 is off (as opposed to a "normal"
stroboscope where the observation is typically made during the
light-on periods). By using this "stroboscopic" technique, the
lighting unit 130 can reliably measure the level of the ambient
light 195 and efficiently adjust the brightness of the emitted
light 190 based on the measured ambient light 195.
[0018] The power for the lighting unit 130 is received from power
source 110. The power source 110 can provide AC power, for example,
from a standard power outlet. In one implementation, the power
source 110 provides a 120V AC power at 60 Hz. Alternatively, the
power source 110 can provide 220V AC power at 50 Hz, or any other
AC power traditionally used at a particular location. For example,
the power source 110 can include a dimming circuit (not shown) that
allows users to manually change the voltage or current provided by
the power source 110. Thus, the lighting system 100 can be
installed anywhere where such a traditional external power is
available. Alternatively, the power source 110 can provide DC
power, for example, from a battery or a solar panel. Thus, the
lighting system can be installed away from standard power outlets.
Although the power source 110 is shown separate from the light
fixture 120, it can be installed inside the light fixture 120, for
example by using a battery or a solar panel so that no external
power source is required for the lighting system 100.
[0019] The lighting unit 130 is held in place by the light fixture
120. For example, the light fixture 120 can be installed at a
permanent location in a building and configured to receive a
matching base part of a housing of the lighting unit 130. In one
implementation, the light fixture 120 is configured so that the
lighting unit 130 can be easily replaced by a user. For example,
the light fixture 120 can include a standardized light fixture
configured to receive and hold traditional light bulbs and the
lighting unit 130 can have a corresponding base, such as a base
with a spiral groove ("Edison screw," e.g., E10, E14, or E27) or a
twist-lock mechanism ("bayonet"), configured to match the receiving
part of those traditional light fixtures. In specific embodiments,
the lighting unit 130 can be implemented in a traditional light
bulb housing, including general (A series), reflector (R series),
bulged reflector (BR series), parabolic aluminized reflector (PAR
series), globe (G series), tube or any other traditional designs
(such as BA, CA, ER, F, FL, P, PR, PL, PS series). Using a
standardized light fixture 120 provides a convenient way to install
the lighting system 100 simply by replacing a traditional light
bulb with the lighting unit 130 without replacing any wiring in a
traditional lighting system. Alternatively, the light fixture 120
can include a non-conventional light fixture especially configured
to receive and hold the lighting unit 130. In other
implementations, the lighting unit 130 can be held by a portable
structure instead of the light fixture 120.
[0020] The light fixture 120 is further configured to provide
electric connection between the external power source 110 and the
lighting unit 130. For example, the light fixture 120 can be
configured to provide a two-point electric contact for AC or DC
power. The light fixture 120 can also provide additional electric
contacts, for example, to control the brightness of the lighting
unit 130. In alternative implementations, the light fixture 120 can
include other electric components, such as an internal power
source, an AC/DC converter, or other power circuits.
[0021] The lighting unit 130 provides the emitted light 190 from
the intermittent light source 132. The light source 132 can include
light emitting diodes (LEDs), organic LED (OLEDs), laser diodes
(LDs), or any other light source that can emit intermittent light
190 whose brightness is substantially lowered (e.g., turned off)
for short time periods. Advantageously, the interruption of the
emitted light 190 can be limited so that the lack of the emitted
light 190 is not directly noticed by the human eye. For example,
the light 190 can have hundreds or thousands of intermittent
periods per second so that the human eye will notice only the
average brightness, but not any flicker effect from the individual
off periods. In alternative implementations where the human
perception has less relevance, the emitted light 190 can be
interrupted for longer periods.
[0022] The ambient light meter 134 can include a photodiode, a
phototransistor, a photoresistor or any other photosensitive
element that can provide an electric signal to indicate a level of
the ambient light 195. In one embodiment, the ambient light meter
134 uses an infrared sensor, where ambient light is estimated based
on data sensed by the infrared sensor. The ambient light meter 134
can include "walls" or "fences" or some optics that limit the
"view" of the light meter 134 and prevent the emitted light 190 to
directly enter the light meter 134. The emitted light 190, however,
can be reflected by objects near the lighting unit 130 and such
reflections may enter the light meter 134 and modify the result of
the ambient light measurement. As the arrangement of such
reflecting objects are often not known before the installation of
the lighting system 130, the corresponding reflections cannot be
easily accounted for at the design stage and the measurements of
the ambient light meter 134 may become unreliable.
[0023] To provide a reliable ambient light measurement, the
lighting unit 130 includes a synchronization mechanism 136 that
synchronizes the ambient light measurements with the intermittent
periods of the light source 132. For example, the synchronization
mechanism 136 can provide a synch signal (which, based on the
"inverse" stroboscopic analogy, could be termed as a "strobe"
signal), that causes a temporary turn-off of the light source 132
as well as taking a sample of the ambient light 195 by the light
meter 134 during the turn-off period. Alternatively, or in
addition, the intermittent light source 132 can have its own,
independent turn-off periods (e.g., a duty cycle), and the
synchronization mechanism 136 can select some of these turn-off
periods to cause the light meter 134 to take sample measurements of
the ambient light 195. Thus, the lighting unit 130 can reliably
measure the ambient light 195 and adjust the emitted light 190
accordingly.
[0024] FIG. 2 is a schematic block diagram that illustrates a
lighting unit 200 according to one embodiment. The lighting unit
200 can be used in lighting systems, such as lighting system 100
shown in FIG. 1, to emit light whose brightness can be adjusted
according to the level of ambient light near the lighting unit. For
example, the lighting unit 200 can be implemented in a housing of a
traditional light bulb and installed in a traditional light fixture
in order to save energy without any additional wiring. The lighting
unit 200 can also be implemented in non-standard housing for
special applications or for portable lighting systems.
[0025] The lighting unit 200 includes a power circuit 210, a
lighting controller 220, an LED driver 230, an LED component 240,
and a light sensor 250. The power circuit 210 receives external
power 205, converts that power to a corresponding appropriate
format for each of the lighting controller 220, the LED driver 230,
and the light sensor 250. The lighting controller 220 receives a
light intensity signal from the light sensor 250 and controls the
LED driver 230 based on the received light intensity signal. The
LED component 240 includes one or more light emitting diodes (LEDs)
to emit light and the LED driver 230 provides power from the power
circuit 210 to the LED component 240 according to the control from
the lighting controller 220.
[0026] The power circuit 210 can include one or more power
converters, such as rectifiers and switching power circuits, to
provide an appropriate power to each element of the lighting unit
200. For example, the power circuit 210 can include diodes and
capacitors for the rectifiers, and a high frequency oscillator, a
switching controller, and one or more power switches, such as power
MOSFETs, for the switching power circuits. The power circuit 210
can be implemented, e.g., on a printed circuit board.
[0027] In one implementation, the external power 205 includes a
100-250 Volt AC power at 50-60 Hz, and the power circuit 210
includes a rectifier, such as a bridge rectifier, to rectify the
received AC voltage into DC voltage. The power circuit 210 also
includes voltage regulators to convert the rectified DC voltage to
a driving voltage, e.g., to about 140 Volt DC power that is
provided to the LED driver 230, and to a low voltage, e.g., to
about 3 Volt DC power that is used to power the lighting controller
220 and the light sensor 250. In alternative implementations, the
external power 205 can include a DC power, and the power circuit
210 can convert that DC power to a driving voltage level for the
LED driver and one or more low level voltages as required by the
lighting controller 220 and the light sensor 250.
[0028] The LED driver 230 uses the drive power from the power
circuit 210 to drive the LEDs in the LED component 240 to emit
light in a controlled manner. For example, the LED driver 230 can
set and maintain a specific current that flows through the LEDs in
the LED component to emit light at a particular brightness.
Alternatively or in addition, the LED driver 230 can intermittently
turn on or off the current that flows through the LEDs in the LED
component 240, thus producing intermittent light emission. Such an
intermittent light emission can extend the life of the LEDs and
provide periods when the ambient light can be accurately measured
without interference from the light emitted by the LED
component.
[0029] The light sensor 250 can include one or more photosensors,
such as photodiodes, phototransistors, photoresistors or any other
photosensitive elements that can provide light intensity signals to
indicate a level of the ambient light. Typically, the light sensor
250 has a decay time that characterizes how fast of changes that
the light sensor is capable of detecting. Changes that happen
faster than the decay time are not directly detected, but only
through their averaged value. The decay time can be, for example,
in a range of about a hundred microseconds (.mu.s) to about several
hundreds of microseconds (.mu.s) depending on the photosensor used
in the light sensor 250. For example, the light sensor can have a
decay time in a range of about 100 .mu.s to about 500 .mu.s. The
decay time may also depend on the environment of the light sensor
250. For example, if the light sensor 250 is near surfaces where
the light can be "bounced" around by reflective surfaces, the decay
time is increased. In the lighting unit 200, the lighting
controller 220 can take into account the decay time of the sensor
250 to improve the ambient light measurement. For example, the
lighting controller 220 can provide an intermittent period for the
ambient light measurement based on the decay time of the light
sensor 250.
[0030] The light sensor 250 also can have wideband or a narrowband
spectral response. For example, the light sensor 250 can have a
photopic response that is designed to approximate the response of
the human eye. If the light sensor 250 has a broader or narrower
spectral response than the human eye, the lighting controller 220
can apply appropriate corrections to approximate the measured
brightness to that as perceived by humans. Alternatively, the
lighting controller 220 does not perform any correction for human
perception. For example, the lighting unit 200 can have direct user
control to set a desired level of brightness and the lighting
controller 220 is configured to maintain that brightness level.
Also, the lighting unit 200 can be used in applications where the
human perception is not critical.
[0031] The light sensor 250 can include "walls" or "fences" or some
optics that limit the "view" of the light sensor 250. For example,
the light sensor 250 can include multiple photosensors each of
which is configured to have a different "view." For example,
different sensors can receive signals from different directions. Or
different sensors can have corresponding optics to collect light
from different distances.
[0032] The lighting controller 220 includes an LED controller 222,
a measuring component 224, and a synchronization mechanism 226. The
measuring component 224 receives one or more light intensity
signals from the light sensor 250 and generates ambient light
measurements 225 based on the received light intensity signals. The
measuring component 224 provides the ambient light measurements 225
to the LED controller 222, which generates a drive control signal
to control the LED driver 230 based on the ambient light
measurements 225. The LED controller 222 is configured to instruct
the LED driver 230 to turn off the LED component 240 for
intermittent time periods. The synchronization mechanism 226 is
configured to synchronize the time when the ambient light
measurements 225 are taken with the intermittent time periods of
the LED component 240.
[0033] In one implementation, the synchronization mechanism 226
generates a measurement synch signal that is used by to the
measuring component 224 to time the measurement (sampling) of the
light intensity signals from the light sensor 250. (As discussed
above, such a measurement synch signal could also be termed as a
"strobe" signal based on the "inverse" stroboscopic analogy.) The
synchronization mechanism 226 also provides the measurement synch
signal to the LED controller 222 to cause a temporary turn-off of
the LED component 240 when the measuring component 224 takes a
sample of the light intensity signals from the light sensor 250. In
one implementation, the synchronization mechanism 226 can be
configured to cause a temporary turn-off period of the LED
component 240 with a duration that is determined based on the decay
time of the light sensor 250. For example, the measuring component
224 can measure the decay of the light sensor 250 and the lighting
controller 220 can adjust the temporary turn-off period caused by
the synchronization mechanism 226 based on the measured decay.
[0034] The synchronization mechanism 226 can generate the
measurement synch signal according to a predetermined scheme. For
example, the synchronization mechanism 226 can generate a periodic
measurement synch signal with a suitably selected period that can
range from a fraction of a second to several seconds depending on
the specific application where the lighting unit 200 is used. If
the lighting unit 200 receives a periodic AC external power 205,
the synchronization mechanism 226 can synchronize the periodic
measurement synch signal with the periodic AC external power 205.
Alternatively or in addition, the synchronization mechanism 226 can
generate a random measurement synch signal. Such a random
measurement can be used in an environment where other light sources
might have periodic fluctuations which may distort the ambient
light measurement.
[0035] Alternatively or in addition to turning off the LED
component 240 according to the measurement synch signal, the LED
controller 222 can have its own, independent turn-off periods, and
the synchronization mechanism 226 can select some of these turn-off
periods to cause the measuring component 224 to take sample
measurements 225 of the light intensity signals from the light
sensor 250. Thus, the lighting unit 200 can reliably measure the
ambient light and adjust the light emitted by the LED component 240
accordingly.
[0036] FIG. 3 is a schematic block diagram illustrating a measuring
component 300 for a lighting unit according to one embodiment. The
measuring component 300 can be implemented, for example, in the
lighting controller 220 of the lighting unit 200 shown in FIG. 2.
In alternative implementations, the measuring unit 300 can be
implemented separate from lighting units, for example, in a light
fixture.
[0037] The measuring component 300 includes an ambient light
measurement element 310 that provides measured light intensity
samples 315 based on light intensity signals 330 and a measurement
synch (strobe) signal 320. The measuring component 300 also
includes element 340 for other measurements based on other signals,
e.g., from occupancy or chemical detectors. The measured light
intensity samples 315 can provide ambient light measurements for an
LED controller, such as LED controller 222 shown in FIG. 2, to
adjust brightness of emitted light. The element 340 for other
measurements can also provide measurement samples to the LED
controller and used to adjust the emitted light.
[0038] The ambient light measurement element 310 can receive the
measurement synch signal 320 from a synchronization mechanism such
as synchronization mechanism 226 shown in FIG. 2. The ambient light
measurement element 310 can be configured to recognize a
predetermined event in the synch signal 320 and take a sample 315
of the light intensity signal 330 in response to such predetermined
event. For example, the ambient light measurement element 310 can
be configured to recognize a falling or rising edge of the synch
signal 320 and take a sample 315 of the light intensity signal 330
in response to the detection of such an edge. Or, the ambient light
measurement element 310 can be configured to recognize a
predetermined voltage level of the synch signal 320 and take a
sample 315 of the light intensity signal 330 in response to the
detection of such a predetermined level. The ambient light
measurement element 310 can take the sample 315 of the light
intensity signal 330 without any further delay or with a
predetermined delay after the event in the synch signal 320 is
detected. In one implementation, the delay to take the sample is
determined based on the decay characteristics of the light sensor
from which the light intensity signal 330 is received.
[0039] The ambient light measurement element 310 can provide the
measured light intensity samples 315 to another component, such as
an LED controller, in order to adjust the light emitted by a
lighting unit. The measured light intensity signals 315 can be
provided with additional information related to the measurement.
For example, the additional information can indicate a spectral
response of the light sensor which provided the light intensity
signal 330. Or, the ambient light measurement element 310 can take
the samples 315 in response to different type of events (such as
both at the rising and falling edges) in the synch signal 320 and
provide the associated type of event along with the particular
sample. Or the ambient light measurement element 310 can take the
samples with different delays from a specific event in the synch
signal 320, and provide the associated delay along with those
samples. The ambient light measurement element 310 can also
determine a decay in the samples 315 measured with different
delays, and provide the calculated decay along with the samples
315. Alternatively or in addition, the calculated decay can be used
to adjust the synch signal 320 to provide sufficient time for
clearing any transient effects before taking the samples.
[0040] The element 340 for other measurements can receive other
intensity signals 345 from additional sensors, such as occupancy,
chemical, temperature, or humidity sensors. For example, a signal
345 from a motion or infrared sensor can provide measurement
information 340 about occupancy near that sensor. Or a signal 345
can be received from a carbon monoxide (CO) or carbon dioxide (CO2)
sensor to provide measurement information 340 about the safety of
the environment near that sensor.
[0041] FIG. 4 is a schematic block diagram illustrating an LED
controller 400 for a lighting unit that includes LEDs to generate
light according to one embodiment. For example, the LED controller
400 can be implemented in the lighting controller 220 of the
lighting unit 200 to control the LED driver 230 shown in FIG. 2. In
alternative implementations, the LED controller 400 can be
implemented separate from lighting units, for example, in a light
fixture.
[0042] The LED controller 400 includes a pulse width modulation
(PWM) signal generator 410, a measurement and control logic 420, a
current controller 430 and an inhibitor 440. The measurement and
control logic 420 receives measured light intensity samples 460
and, optionally, other samples 470, and uses those samples to
generate one or more timing parameters 415 for the PWM signal
generator 410 and one or more amplitude parameters 435 for the
current controller 430. Based on the timing and amplitude
parameters 415 and 435, the PWM signal generator 410 and the
current controller 430 generate drive control signals 480 for an
LED driver. The inhibitor 440 in the LED controller 400 receives a
synch signal 450 and uses the received synch signal 450 to instruct
the PWM signal generator 410 to generate drive control signals 480
that inhibit light emission for intermittent time periods. Such
intermittent periods of no emitted light can be used to measure
ambient light levels more accurately.
[0043] The PWM signal generator 410 can generate an alternating
drive control signal 480 to turn on and off the LEDs based on the
timing parameters 415. In one implementation, the PWM signal
generator 410 generates a periodic square signal and the timing
parameters 415 determine the periodic signal's frequency and a
corresponding duty ratio. The duty ratio is the ratio of the
durations of the on and off periods within the periodic signal.
Thus, the timing parameters 415 determine the duty ratio of the PWM
drive control signal 480 which, in turn, determines the overall or
average brightness of the driven LEDs. In particular embodiments,
the periodic PWM drive control signal 480 can have a frequency of a
few hundred Hz (i.e., number of periods per second) or few hundred
kHz. For example, the frequency of the PWM drive control signal 480
can be between about 100 Hz and about 100 kHz. In alternative
implementations, the PWM signal generator 410 can generate a
non-periodic drive control signal 480, such as a pseudo random
alternating signal with a desired average frequency and average
duty ratio.
[0044] The PWM signal generator 410 also receives a signal from
inhibitor 440. The inhibitor 440 is configured to inhibit the PWM
drive control signal 480 by putting it into an off position for a
time period as determined by the synch signal 450. In one
implementation, the inhibitor 440 is configured to recognize a
predetermined event in the synch signal 450 and to inhibit the PWM
drive control signal 480 in response to such a predetermined event.
For example, the inhibitor 440 can be configured to recognize
rising and falling edges of the synch signal 450 and inhibit the
PWM drive control signal 480 between a rising and a subsequent
falling edge of the synch signal. Or, the inhibitor 440 can be
configured to detect a voltage level of the synch signal 450 and
inhibit the PWM drive control signal 480 while the detected voltage
is above such a predetermined level. The inhibitor 440 can also
inhibit the PWM drive control signal 480 for a predetermined time
period after detecting a corresponding event (e.g., a rising edge)
in the synch signal 450. The predetermined period of the inhibition
can be selected based on the time, e.g., a typical light sensor
decay time required for an ambient light measurement. Thus, during
the off period, the LEDs do not emit light and the ambient light
can be more accurately measured.
[0045] In addition to the PWM signal from generator 410, the drive
control signals 480 can include a current control signal that is
generated by the current controller 430 based on the amplitude
parameter 435. The current control signal from the current
controller 430 is configured to determine the current which passes
through the LEDs and thus can be used to control the brightness of
the LEDs. In one implementation, the PWM signal is used to turn on
and off the LEDs and the current control signal is used to control
the current that passes through the LEDs when they or turned on.
Thus, the brightness of the light emitted by the LEDs can be easily
controlled as required by a particular application, such as dimming
the emitted light according to an ambient light level or as
instructed by a user input.
[0046] The measurement and control logic 420 receives the measured
light intensity samples 460 that can indicate the level of ambient
light and, based on the received samples 460 and reference settings
425, determines the timing parameters 415 for the PWM signal
generator 410. Optionally, the measurement and control logic 420
can also determine the amplitude parameters 435 for the current
controller 430. The measurement and control logic 420 can implement
a functional relationship between the ambient light intensity
samples 460 and the timing parameters 415 as required for specific
implementations.
[0047] In one implementation, the measurement and control logic 420
determines representative values, e.g., averages, of the received
light intensity samples 460 and uses those representative values to
adjust the duty ratio of the PWM drive control signal 480 through
the timing parameters 415. For example, the measurement and control
logic 420 can calculate a representative value based on a moving
average over a predetermined number (e.g., 5-10 samples) of the
latest light intensity samples 460. Instead of or in addition to
the moving average, the measurement and control logic 420 can use
other filters, such as median filters, to determine the
representative values of the light intensity samples. Then, the
measurement and control logic 420 compares the representative
values of the samples 460 to corresponding reference settings 425
to determine the timing parameters 415 so that a desired
illumination is provided by the controlled LEDs.
[0048] In particular embodiments, the measurement and control logic
420 is configured to set the timing parameters 415 so that the
controlled LEDs are turned off if the representative values of the
light intensity samples 460 are above a reference level determined
by the reference settings 425, thus indicating that the ambient
light provides sufficient illumination. On the other hand, if the
representative values of the ambient light intensity samples 460
are below the reference level determined by the reference settings
425, the timing parameters 415 are set to provide an increased duty
ratio (i.e., more "on" time). Thus, the controlled LEDs emit more
light when the ambient light is low. The measurement and control
logic 420 can implement an inverse relationship between the
measured ambient light intensity and the duty ratio (consequently
the brightness) of the LEDs controlled by the LED controller 400.
This inverse relationship can be linear or it can have some other
monotonic functional form. Alternatively or in addition to the
timing parameters 415, the measurement and control logic 420 can be
configured to set the amplitude parameters 435 to achieve the
desired illumination.
[0049] The reference settings 425 in the measurement and control
logic 420 represent parameters, such as one or more reference
ambient light levels, that can be used to define the functional
relationship between the measured light intensity samples 460 and
the corresponding timing and amplitude parameters 415 and 435 for
the drive control signals 480. The reference setting 425 can have
preset values or values set by the user. For example, the LED
controller 400 can receive user settings from a manual control in a
lighting switch through a wired or wireless connection. The LED
controller can also receive settings from control devices, such as
computers running a software application to control lighting
levels. Or the LED controller 400 can be implemented in a lighting
unit that includes manually actuated switches or buttons to receive
user input setting a desired light level.
[0050] In one implementation, the measurement and control logic 420
receives additional information related to the light intensity
samples 460. For example, the additional information can include
relative delays between a set of subsequently measured light
intensity samples 460. Or, the additional information can
characterize spectral (bandwidth) or dynamic (decay) properties of
the light sensor that was used to measure the intensity of the
ambient light. Thus, the measurement and control logic 420 can be
configured to adjust the drive control signals 480 using this
additional information. For example, the light intensity samples
460 can be processed to correct the undesirable effects of narrow
band or slow light sensors. In one implementation, the measurement
and control logic 420 is configured to calculate the decay of the
light sensor from subsequent samples 460 measured during the same
intermittent off period with different delays.
[0051] The measurement and control logic 420 can also receive other
measurement samples 470, for example, from an occupancy detector or
a chemical detector, and use these samples 470 to adjust the timing
and amplitude parameters 415 and 435 to alter the light emitted by
the controlled LEDs. For example, the measurement and control logic
420 can turn off the controlled LEDs if the samples 470 include
measurements from the occupancy detector indicating that nobody is
around. Or the measurement and control logic 420 can visibly and
periodically alter the brightness or color of the controlled LEDs
to provide a warning if the samples 470 include measurements from
the chemical detectors indicating that dangerous chemicals are
around and thus the environment is not safe.
[0052] FIG. 5 is a schematic block diagram illustrating a system
500 for intermittent driving of LEDs in a lighting unit according
to one embodiment. The system 500 can be implemented, for example,
in the lighting unit 200 shown in FIG. 2. In alternative
implementations, the system 500 can be implemented in a combination
of a lighting unit and a light fixture.
[0053] The system 500 includes a power circuit 510 that powers an
LED component 520 through an LED driver 530 to emit light 590. In
the system 500, the LED driver 530 receives drive control signals
550 that control the current through the LED component 520, and
thus the brightness of the emitted light 590. In particular, the
LED component, the LED driver 530, and the drive control signals
550 are configured to generate intermittent periods when the
brightness of the emitted light 590 is lowered, e.g., turned off,
for a short time. Such intermittent driving system 500 can provide
for accurate ambient light measurements during the off periods. As
the driving current is not flowing continuously, the intermittent
driving system 500 can also extend the life of the LEDs in the LED
component 520.
[0054] In the LED driving system 500, the LED component 520 and the
LED driver 530 are coupled in series with the power circuit 510.
The power circuit 510 provides DC power to the LED component 520
such that a DC current flows through the LED component 520 and the
LED driver 530 back to the power circuit 510. For example, the
power circuit 510 can convert standard AC power, e.g., a 120 V AC
power at 60 Hz, from a wall outlet to provide a DC power in the
range of about 100 V to about 200 V. Or the power circuit 510 can
provide the DC power from a portable power source, such as a
battery or a solar panel.
[0055] The LED component 520 includes one more LEDs that emit the
light 590 as the DC current is flowing through those LEDs. The LEDs
in the component 520 can include semiconductor structures, such as
GaN or GaAs based LEDs, or organic light emitting diodes (OLEDs).
In particular implementations, the LED component 520 can provide
white light or any colored light as required for a specific
implementation. For example, the LED component 520 can include LEDs
of different colors that can be combined to emit light with a
specific color temperature. Thus, the LED component 520 can provide
color temperature shifting.
[0056] The LED driver 530 includes a switch 534 coupled in series
with the LED component 520. In one embodiment, the switch 534
includes a power MOSFET which can efficiently turn on and off the
DC power current. In alternative implementations, the switch 534
can include any other power switch such as diodes, JFETs, IGBT,
BJT, thyristors. Although the switch 534 has been illustrated at a
specific part of the driving system 500, it can be located
elsewhere, for example in the power circuit 510 and perform the
same function of turning off the LED component 520. For example,
the switch may be connected to the primary winding of a
transformer, while the LED is connected to the secondary winding of
the transformer.
[0057] The switch 534 is turned on or off according to a pulse
width modulated (PWM) drive control signal 552. Thus, the DC
current from the power circuit 510 may flow through the LED
component 520 when the switch 534 is turned on by the PWM signal
552, but no (or minimal) current can flow through the LED component
520 when the switch 534 is turned off by the PWM signal. The PWM
drive control signal 552 can turn on and off the LED component 520
at a high frequency (e.g., 1-100 kHz so that the individual
intermittent off periods of the emitted light 590 are not directly
observed by the human eye. Instead, the human eye perceives only an
average brightness that is proportional to the duty ratio of the
PWM drive control signal.
[0058] The LED Driver 530 in the LED driving system 500 also
includes a current sink 538 coupled in series with the switch 534
and the LED component 520. The current sink 538 is configured to
control the amount of current that flows through the LED component
520 back to the power circuit 510. In particular, the current sink
538 receives a current control drive signal 554 that determines the
amount of DC current that can flow back to the power circuit 510.
As the brightness of the LEDs in the LED component 520 depends on
the amount of the DC current, the current control drive signal 554
can also be used for controlling the brightness of the emitted
light 590. Alternatively or in addition, a current source or other
current limiting circuit can be used to control the amount of DC
current that flows through the LED component 520.
[0059] FIG. 6 includes schematic diagrams illustrating traces of a
pulse width modulated (PWM) drive control signal 610, a measurement
synch signal 620 and a light intensity signal 630 as a function of
time according to one embodiment. The PWM drive control signal 610
and the measurement synch signal 620 can be generated by a lighting
controller, and the light intensity signal 630 can be generated by
a light sensor in a lighting unit, such as the lighting controller
220 and the light sensor 250 in the lighting unit 200 shown in FIG.
2. For example, the PWM drive control signal 610 can be generated
by the LED controller 222 to control the LED driver 230 and the
measurement synch signal 620 can be generated by the
synchronization mechanism 226.
[0060] The signals 610, 620 and 630 illustrate an implementation of
using the measurement synch signal 620 to synchronize the PWM drive
control signal 610 with an ambient light measurement (sampling) 660
of the light intensity signal 630. The PWM drive control signal 610
includes regular turn-on and turn-off periods 614 and 616 to turn
on and off the driven LEDs according to a specific duty ration and
thus intermittently emit light with a corresponding average
brightness. The PWM drive control signal 610 also includes a
measurement turn-off period 640 to turn off the driven LEDs so that
no light is emitted when the ambient light measurement 660
happens.
[0061] The trace of the light intensity signal 630 illustrates how
the signal from the light sensor changes as a result of turning on
and off the emitted light by the PWM drive control signal 610. For
example, as the light is turned off at the beginning of the
turn-off period 640, the light intensity signal 630 shows a gradual
decay 634 to an ambient light level 636. As the light is turned on
at the end of the turn-off period 640, the light intensity signal
630 shows a gradual increase to a higher light intensity,
indicating that the light emitted by the driven LEDs is detected by
the light sensor in addition to the ambient light. The light
intensity signal 630 shows similar gradual decrease and increase
characteristics at the next turn-off period 616 when the light is
turned off and on.
[0062] The measurement turn-off period 640 is triggered by a rising
edge 622 of the measurement synch signal 620. The rising edge 622
inhibits the PWM drive control signal 610 for a predetermined
duration that corresponds to the duration of the turn-off period
640. The following falling edge 624 of the measurement synch signal
620 triggers the measurement (sampling) 660 of the light intensity
signal 630. The time delay between the rising and falling edges 622
and 624 of the synch signal 620 is shorter than the predetermined
duration of the measurement turn-off period 640 in the LED drive
signal 610. Thus, the measurement 660 triggered by the falling edge
of the synch signal is taken when the light is still turned off.
Furthermore, the time delay between the rising and falling edges
622 and 624 of the synch signal 620 is longer than the decay time
of the light intensity signal 630. Accordingly, the measurement 660
can accurately represent the ambient light level 636.
[0063] FIG. 7 includes schematic diagrams illustrating traces of a
pulse width modulated (PWM) drive control signal 710, a measurement
synch signal 720 and a light intensity signal 730 as a function of
time according to another embodiment. The PWM drive control signal
710 and the measurement synch signal 720 can be generated by a
lighting controller, and the light intensity signal 730 can be
generated by a light sensor in a lighting unit, such as the
lighting controller 220 and the light sensor 250 in the lighting
unit 200 shown in FIG. 2. For example, the PWM drive control signal
710 can be generated by the LED controller 222 to control the LED
driver 230 and the measurement synch signal 720 can be generated by
the synchronization mechanism 226.
[0064] The signals 710, 720 and 730 illustrate an implementation of
using the measurement synch signal 720 to synchronize an ambient
light measurement 760 of the light intensity signal 730 with the
PWM drive control signal 710. The PWM drive control signal 710
includes turn-on and turn off periods 714 and 716 to turn on and
off the driven LEDs according to a specific duty ratio and thus
intermittently emit light with a corresponding average brightness.
The PWM drive control signal 710 also includes a measurement
turn-off period 740 to turn off the LED component so that no light
is emitted when the ambient light measurement 760 happens.
[0065] The trace of the light intensity signal 730 illustrates how
the signal from the light sensor changes as a result of turning on
and off the emitted light. In the example of FIG. 7, as the light
is turned on and off before the turn-off period 740, the light
intensity signal 730 has a substantially constant value indicating
that the light sensor is relatively slow and measures only the
average illumination level. At the beginning of the measurement
turn-off period 740, the light intensity signal 730 shows a slow,
gradual decay 734 to an ambient light level 736. As the light is
turned on at the end of the turn-off period 740, the light
intensity signal 730 shows a gradual increase to a higher light
intensity, indicating that the light emitted by the LED component
is detected by the light sensor in addition to the ambient light.
The light intensity signal 730, unlike the light intensity signal
630 in the example of FIG. 6, can not detect the individual
turn-off periods 716 because their duration is shorter than the
characteristic decay time of the light sensor producing the light
intensity signal 730.
[0066] The measurement turn-off period 740 is triggered by a rising
edge 722 of the measurement synch signal 620. The rising edge 722
inhibits the PWM drive control signal 710 until the subsequent
falling edge 724 of the synch signal 720. The rising edge 722 of
the measurement synch signal 720 also triggers the measurement
(sampling) 760 of the light intensity signal 730 after a
predetermined delay. The time delay between the rising edge 722 and
the measurement 760 is configured to be shorter than the time
between the rising and falling edges 722 and 724 of the synch
signal 720 which inhibits the LED drive signal 710 during the
turn-off period 740. Thus, the measurement 760 triggered by the
rising edge 722 of the synch signal 720 is taken when the light is
still turned off. Furthermore, the time delay between the rising
edge 722 and the measurement 760 is longer than the decay time of
the light intensity signal 730. Accordingly, the measurement 760
can accurately represent the ambient light level 736.
[0067] In alternative implementations, the measurement 760 can be
taken before the light intensity signal 730 fully settles to the
ambient light value 736, and the measured value can be corrected
based on the decay 734 of the light intensity signal 734.
[0068] FIG. 8 is a schematic flow chart illustrating a method for
operating a lighting system according to one embodiment. The method
800 can be implemented by a lighting unit that includes LEDs to
emit light, such as the lighting unit 200 that includes the LED
driver 230 to drive the LED component 240 by power from the power
circuit 210 to emit light as shown in FIG. 2. The lighting unit
also includes control circuitry, such as the lighting controller
220 and the light sensor 250 to control the LED driver 230 and thus
the light emitted by the LED component 230 in the lighting unit 200
(FIG. 2).
[0069] According to the method 800, the lighting unit receives
external power (step 810). The external power can be received from
a regular wall outlet, from a battery, a solar panel or any other
power source, e.g., when a user turns on the lighting system. In
the lighting unit 200 of FIG. 2, for example, the external power
205 is received by the power circuit 210 that is configured to
convert the received external power to the different levels as
required by the different parts of the lighting unit.
[0070] Next, the lighting unit initializes its lighting controller
(step 820). In one implementation, the lighting controller includes
a microcontroller having a central processing unit and memory,
including non-volatile memory. The non-volatile memory can store
programs (i.e., software instructions) to operate the lighting
controller. In the lighting unit 200 of FIG. 2, for example, the
microcontroller can initialize programs implementing the LED
controller 222, the measuring component 224, and the
synchronization component 226. For example, the microcontroller can
load the programs into active memory, initialize their parameters,
and initialize their connections.
[0071] After initialization, the lighting controller in the
lighting unit turns on drive control signals to drive the LEDs
(step 830). In the lighting unit 200 of FIG. 2, for example, the
LED controller 222 can provide the drive control signals to the LED
driver 230 that drives the LEDs in the LED component 240. In one
implementation, the drive control signals include pulse width
modulated (PWM) signals to turn the LEDs on and off alternately
according to a predetermined frequency and duty ratio. The lighting
controller can also turn on a current control signal to set the
level of current flowing through the LEDs. In particular
embodiments, the lighting controller can turn on the driver control
signals so that the LEDs start operating at a predetermined level
of illumination. For example, the lighting controller can turn on
the LEDs at 50% to 80% level to give a quick response to the user
who switched on the lighting unit, and to maintain the possibility
for adjusting the lighting unit's brightness either up or down.
Alternatively, the LEDs can be turned on at a maximum or a minimum
brightness level. In one implementation, the drive control signals
turn off the LEDs until later instructions.
[0072] The lighting controller in the lighting unit turns on a
measurement synchronization mechanism (step 840). In the lighting
unit 200 of FIG. 2, for example, the synchronization mechanism 226
can start generating measurement synch (strobe) signals that
trigger measurements of the ambient light level. Or the
synchronization mechanism can use the off periods of a PWM drive
control signal to schedule ambient light level measurements.
[0073] The lighting controller in the lighting unit measures light
intensity signals from an ambient light sensor in synch with
intermittent off periods in the drive control signal (step 850). In
the lighting unit 200 of FIG. 2, for example, the synchronization
mechanism 226 generates measurement synch (strobe) signals that
intermittently turn off (or substantially reduce) the LED power and
trigger measurements (sampling) of the light intensity signal from
the light sensor 250 during the intermittent off periods. Or the
synchronization mechanism can use the off periods of a PWM drive
control signal of the LEDs to schedule measurements (sampling) of
the light intensity signal from the light sensor 250 during those
off periods. Due to the synchronization of the intermittent off
periods in the LED drive and the measurements (sampling) of the
light intensity signal from the light sensor 250, the ambient light
level can be more accurately measured.
[0074] The lighting controller in the lighting unit processes the
measured light intensity signals to determine whether the
brightness of the LEDs should be changed (decision 860). In the
lighting unit 200 of FIG. 2, for example, the LED controller 222
can filter, e.g., average, the measured light intensity signals and
use those processed measurements to determine whether the
brightness should be changed. This processing can also correct
systematic distortions, e.g., those caused by the light sensor, in
the measured light intensity samples. The decision 860 can be based
on reference settings that can be preset at the time of manufacture
or set by users. The reference settings can define thresholds for
turning on or off the lighting unit or to define appropriate
adjustments to different ambient light levels. In one
implementation, the lighting unit can include communication
circuitry to receive the reference settings from a user even when
the lighting unit is installed, thus the processing of the measured
light intensity samples can be changed according to the user's
instructions.
[0075] If the brightness of the LEDs should be changed (YES branch
of decision 860), the lighting controller in the lighting unit
adjusts the LED drive control signals (step 870). In the lighting
unit 200 of FIG. 2, for example, the LED controller 222 can adjust
the duty ratio of a PWM drive control signal. Alternatively or in
addition, the LED drive control signals can be adjusted to modify
the current through the LEDs. In one implementation, the lighting
controller can use preprogrammed functions stored in a non-volatile
memory of the lighting unit to determine the type and amount of the
adjustment. For example, the lighting controller can be programmed
to provide an inverse relationship between the measured ambient
light level and a corresponding brightness of the LEDs. If the
lighting unit includes communication circuitry to receive the
reference settings from a user even when the lighting unit is
installed, the brightness of the LEDs can be changed according to
the user's instructions. Thus, the user can set (dim) the level of
illumination.
[0076] After adjusting the LED drive signals (step 870) or if no
change of the LED brightness is required (NO branch of decision
860), the lighting controller in the lighting unit returns to
measuring light intensity signals from an ambient light sensor in
synch with intermittent off periods in the drive control signal
(step 850).
[0077] FIGS. 9A, 9B and 9C are schematic diagrams illustrating
compact lighting units 910, 920, and 930, respectively, according
to different embodiments. The compact lighting units 910, 920, and
930 provide physical arrangements to implement the lighting unit
130 (FIG. 1) or the lighting unit 200 (FIG. 2) that include light
sensors to measure ambient light levels and are configured to
adjust their brightness according to the measured ambient light
levels. Thus, the lighting units 910, 920, and 930 can save energy
without requiring complex and expensive external equipments.
[0078] As shown in FIG. 9A, the lighting unit 910 is implemented in
a light bulb housing 912 having a BR series design with an Edison
base 913 that can be attached to standard light fixtures to provide
external power for the lighting unit 910. The lighting unit 910
includes a power circuit 914, a control circuit 916, an LED
component 918 and a light sensor 919.
[0079] The power circuit 914 converts the external power into
different DC powers as required for the operation of the LED
component 918 as well as for the operation of the control circuit
916 and the light sensor 919. For example, the power circuit 914
can include switching power converters to convert an external AC
power (between about 100V to about 250V at about 50-60 Hz) into a
high DC power (between about 100V and about 300V) for the LED
component 918 and into a low DC power (between about 2V and about
10V) for the control circuit 916 and the light sensor 919. The
power circuit 914 can also include an LED driver to provide the
high DC power for the LED component 918 in a controlled way, e.g.,
in intermittent periods. The power circuit 914 can be implemented
in one or more integrated circuits installed in a printed circuit
board that fits within the housing 912.
[0080] The control circuit 916 can be configured to control the LED
component 918, e.g., through an LED driver implemented in the power
circuit 914, based on ambient light measurements from the light
sensor 919. The control circuit 916 can include a microcontroller
or an application specific IC (ASIC) that can be installed on the
same or a different printed circuit board than the power
circuit.
[0081] In the lighting unit 910, the light sensor 919 is installed
separate from the control circuit 916, in the proximity of the LED
component 918 that is configured to emit light from the housing
912. In the example of FIG. 9A, the lighting unit 910 has no
physical obstruction, such as a "wall" or "fence" that would block
the light emitted by the LED component 918 to enter into the light
sensor 919. Thus, the light sensor 919 may receive the emitted
light directly or indirectly (through reflections) from the LED
component 918. In fact, the light sensor 919 may receive such a
high intensity light from the LED component 918 that, for practical
purposes, no contribution can be detected from an external, ambient
light due to the limited sensitivity of the light sensor 919. Thus,
the control circuit 916 intermittently turns off the LED component
918 so that the light sensor 919 can more accurately sense the
ambient light level in the absence of light from the LED component
918. Based on the measured ambient light intensity, the control
circuit 916 can properly adjust the overall brightness of the
lighting unit 910.
[0082] As shown in FIG. 9B, the lighting unit 920 is implemented in
a light bulb housing 922 having a BR, R or PAR series design with
an Edison base 923 that can be attached to standard light fixtures
to provide external power for the lighting unit 920. The lighting
unit 920 includes a power circuit 924, a control circuit 926, an
LED component 928 and a light sensor 929 that are similar to the
power circuit 914, the control circuit 916, the LED component 918
and the light sensor 919 of the lighting unit 910 discussed above
with reference to FIG. 9A.
[0083] In the lighting unit 920, the light sensor 929 is installed
on the same printed circuit board as the control circuit 926. In
the example of FIG. 9B, the lighting unit 920 has a "light pipe"
925 that blocks the light emitted by the LED component 928 to enter
into the light sensor 929. The light sensor 929, however, may
receive the emitted light indirectly through reflections from the
LED component 928. The illumination level of such reflections may
substantially vary depending on the environment of the lighting
unit 920. Due to these uncontrolled reflections, for practical
purposes, the ambient light level cannot be detected in a reliable
manner. Thus, the control circuit 926 intermittently turns off the
LED component 928 so that the light sensor 929 can more accurately
sense the ambient light level in the absence of light from the LED
component 928. Based on the measured ambient light intensity, the
control circuit 926 can properly adjust the overall brightness of
the lighting unit 920.
[0084] As shown in FIG. 9C, the lighting unit 930 is implemented in
a light bulb housing 932 having a tube style design. The lighting
unit 930 includes a power circuit 934, a control circuit 936, an
LED component 938 and a light sensor 939 that are similar to the
power circuit 914, the control circuit 916, the LED component 918
and the light sensor 919 of the lighting unit 910 discussed above
with reference to FIG. 9A.
[0085] In the lighting unit 930, the light sensor 939 is installed
on an edge of the tube style housing 932 in a way that it is facing
away from the main direction of the light emitted by the LED
component 938. Due to this geometrical design, the light emitted by
the LED component 938 does not directly enter into the light sensor
939. The light sensor 939, however, may receive the emitted light
indirectly through reflections from the LED component 938. The
illumination level of such reflections may substantially vary
depending on the environment of the lighting unit 930. Due to these
uncontrolled reflections, for practical purposes, the ambient light
level cannot be detected in a reliable manner. Thus, the control
circuit 936 intermittently turns off the LED component 938 so that
the light sensor 939 can more accurately sense the ambient light
level in the absence of light from the LED component 938. Based on
the measured ambient light intensity, the control circuit 936 can
properly adjust the overall brightness of the lighting unit
930.
[0086] This application uses examples to illustrate the invention.
The patentable scope of the invention includes other examples.
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